code: def check_unknown_transitions(graph):
      msg = (
          "Step *{0.name}* specifies a self.next() transition to "
          "an unknown step, *{step}*."
      )
      for node in graph:
          unknown = [n for n in node.out_funcs if n not in graph]
          if unknown:
              raise LintWarn(
                  msg.format(node, step=unknown[0]),
                  node.tail_next_lineno,
              )
  
imports: import re
  from .exception import MetaflowException
  from .util import all_equal
label_desc: Use image node_id 8 for calling a global function with example usage: check_unknown_transitions(graph) without return types